Vapor generating apparatus



March 21, 1967 E. G. HUTCHINGS VAPOR GENERATING APPARATUS Filed April 14, 1965 FIG. 2

INVENTOR. Edward G. Hufchings ATTORNEY United States Patent ()fi ice 3,369,872 Patented Mar. 21, 1957 3,309,872 VAPOR GENERATING APPARATUS Edward George Hutchings, Wembley, Middlesex, England, assignor to Babcock & Wilcox Limited, London, England, a corporation of Great Britain Filed Apr. 14, 1965, Ser. No. 448,206 Claims priority, application Great Britain, Apr. 17, 1964, 16,118/ 64 9 Claims. (Cl. 60-104) This invention relates to vapor generating apparatus and particularly to a vapor generating plant in which low pressure vapor is generated by heat derived from high pressure vapor. Such plant is known in which a low pressure boiler is placed above the drum of a high pressure boiler and is arranged so that vapor rises from the high pressure boiler through a pipe leading to heating coils in the low pressure boiler. In the low pressure boiler the vapor is condensed, its latent heat serving to generate low pressure vapor, and the condensate returns under gravity to the low pressure boiler. The output of the low pressure boiler is controlled by varying the firing rate of the high pressure boiler with consequent corresponding changes in the pressure and temperature of the working fluid in that boiler.

In practice the output of the low pressure boiler and hence the pressure and temperature of the working fluid in the high pressure boiler may vary over a wide range and sometimes quite rapidly. Such onerous operating conditions are undesirable and are liable to lead to trouble.

According to the present invention, there is provided a vapor generating plant having means for supplying vapor at high pressure, a low pressure boiler arranged to operate with said high pressure vapor as heating medium, and

valve means arranged to control the rate of flow of high pressure vapor to the low pressure boiler and adapted to adjust the rate of flow automatically in response to the demand on the low pressure boiler.

By way of example, an embodiment of the present invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 is a schematic illustration of a plant suitable for marine installation having a low pressure boiler, arranged in accordance with the invention to operate with high pressure steam;

FIGURE 2 is a side view of the low pressure boiler; and

FIGURE 3 is an end view of the low pressure boiler.

In FIGURE 1, the numeral 1 indicates the steam-andwater drum of a boiler and is such as to deliver steam at high pressure. Steam from the drum 1 passes through a high pressure vapor path along line 2 to U-shaped heating tubes 3 immersed in water in a low pressure boiler 4. The condensate from the tubes 3 returns to the drum 1 through line 5 serving as a condensate discharge path leading from the boiler 4. A pump P may be included in the return line 5. The latent heat of the steam condensing in flowing through the tubes 3 generates further steam, at a lower pressure, from the water surrounding the tubes 3 and is delivered to the point of use through ducts 6.

The rate of flow of high pressure steam to the low pressure boiler is controlled by an adjustable valve 7 in the line 2 near the inlet to the low pressure boiler and tends to maintain the pressure in the drum 1 constant. Adjustment of the setting of the valve 7 is effected automatically in response to variations in load demand on the low pressure boiler, the control being effected through the device 8 responsive to pressure in the vapor space of the low pressure boiler 4. The valve 7 and the device 8 are in communication through a line 9, shown as a dotted line in FIGURE 1.

As is shown in FIGURES 2 and 3, the U-tubes 3 extend in a generally horizontal direction from the drum 3a providing inlet and outlet headers. The normal water level in the low pressure boiler 4 lies just below the upper limit of the bank of tubes 3 and is controlled by the device 10. Steam generated in the boiler 4 passes to the ducts 6 through a scrubber 11. Steam from the ducts 6 may be supplied to oil burners and/or sootblowers for the high pressure boiler; and' in marine installation the steam may be used for other ancillary services. If required, the low pressure steam may be superheated, and a heat exchanger (not shown) utilizing steam from the high pressure boiler may be provided for this purpose.

In a compact plant, the steam drum 1 may supply only the low pressure boiler 4. In other embodiments, however, it may be arranged that the source of high pressure vapor for the boiler 4 also supplies a main load, e.g., a turbine connected in parallel with the boiler 4. Such a turbine is indicated by broken lines at 12 in FIGURE 1.

It will be realized that in the embodiment described, the setting of the valve 7 determines the rate of condensation of high pressure vapor in the low pressure boiler 4. In a modification of this embodiment, shown in phantom on FIGURE 1, the valve 7 may be included in the return line 5 through which condensate passes from the tube 3. The setting of the valve 7 in this case will determine the extent to which the tubes 3 are flooded and, so the proportion of the heat exchange surfaces that are exposed to the high pressure vapor.

Instead of using the pressure in the vapor space of the boiler 4 as representative of the load on the boiler and setting valve 7 to adjust the flow of high pressure steam in dependence upon the pressure, the load may be represented by the flow of vapor from the boiler. Alternatively, therefore, the setting of the valve 7 may be controlled in dependence upon the pressure in, and the rate of flow of vapor from, the boiler 4.

Although the invention hasbeen shown in but several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof as set forth in the following claims.

What is claimed is:

1. Vapor generating plant having means for supplying vapor at high pressure, a low pressure boiler arranged to operate with said high pressure vapor as heating medium, and valve means arranged to control the rate of fiow of high pressure vapor to the low pressure boiler and to adjust the rate of flow automatically in response to the demand on the low pressure boiler.

2. Vapor generating plant as claimed in claim 1, in which the valve means includes a valve disposed in the vapor path through which high pressure vapor flows to the low pressure boiler.

3. Vapor generating plant according to claim 2, in which the valve means includes means responsive to vapor pressure in the low pressure boiler.

4. Vapor generating plant as claimed in claim 1, in which the valve means includes a valve disposed in a condensate discharge path leading from the low pressure boiler.

5. Vapor generating plant according to claim 4, in which the valve means includes means responsive to vapor pressure in the low pressure boiler.

6. Vapor generating plant according to claim 1 including a high pressure boiler for supplying said high pressure vapor to the low pressure boiler and a main load connected in parallel with said low pressure boiler to the high pressure boiler.

7. Vapor generating plant comprising: erated in said low pressure boiler and operatively assoa high pressure boiler providing a source of high presciated with said valve.

sure vapor, 9. Vapor generating plant according to claim 7 ina turbine connected to said high pressure boiler and eluding a device responsive to the flow of generated vapor adapted to be driven by high pressure vapor, 5 from said low pressure boiler and operatively associated a low pressure boiler, With said valve. a line, connected in parallel with said turbine to said high pressure boiler, extending through said low pres- References Cited y the Examine! .sure boiler in heat transfer relationship with a vapor- UNITED STATES PATENTS izable li u' enera' sure 'boi le gid returr x i r i t o s ai c l h i i p r efs ur e 10 1917166 7/1933 Trade et a1 122-33 boner a r 1,940,663 12/1933 Coutant 122-33 2,291,195 7/1942 Stieger 122-33 and means including a valve in said line responsive to demand on said low pressure boiler for automatically controlling the rate of How through sald line. 15 MARTIN P. SCHWADRON Primary Examiner 8. Vapor generating plant according to claim 7 including a device responsive to the pressure of vapor gen- ROBERT BUNEVICH, Examine"- 2,982,263 5/1961 Villiers et al 12232 

1. VAPOR GENERATING PLANT HAVING MEANS FOR SUPPLYING VAPOR AT HIGH PRESSURE, A LOW PRESSURE BOILER ARRANGED TO OPERATE WITH SAID HIGH PRESSURE VAPOR AS HEATING MEDIUM, AND VALVE MEANS ARRANGED TO CONTROL THE RATE OF FLOW OF HIGH PRESSURE VAPOR TO THE LOW PRESSURE BOILER AND TO ADJUST THE RATE OF FLOW AUTOMATICALLY IN RESPONSE TO THE DEMAND ON THE LOW PRESSURE BOILER. 